(a) Field of the Invention
This invention relates to dies for forming cardboard cartons, particularly those having a so-called "reverse cut score".
Methods and apparatus are now known for die cutting paperboard. In addition, tear strips have been produced in paperboard cartons and the like by die cutting the paperboard from opposite sides thereof to provide removable areas which are defined by relatively widely spaced-out creases extending into one surface of the board and more closely spaced-out creases extending in parallel side-by-side relation to the first creases and extending into the opposite side of the sheet. When the intermediate area is grasped, the paperboard splits from one cut crease to the other to permit removal of the defined area. Under normal circumstances, this die-cutting operation is done by first die cutting one side of the sheet and then die cutting the opposite side of the sheet in a separate operation. This method has been followed using cutting presses which were normally provided with a die which was engageable with one side only of the sheet.
Conventionally, dies for cutting and creasing paperboard blanks have been made by setting steel rules for cutting the paperboard in a predetermined pattern between individually cut wood blocks, which are held in a steel frame by wooden wedges with the edges of the rules extending above the blocks. Small blocks of sponge rubber, or synthetic cork were generally placed on each side of the cutting rule to push the board free of the knives on completion of the cutting stroke. The creasing rules, in most systems, are glued to the wooden blocks. Other systems of dies are known in which the steel rules are inserted into grooves cut by jig saw into a slab of plywood of 3/4 inch thickness in a predetermined pattern so that when the plywood die is brought to bear against the paperboard a blank of the desired configuration is stamped out.
In the formation of tear strips of the type employing a peripheral pair of die cut grooves in opposite sides of the paperboard, it was usual practice to have the die cuts or grooves extend approximately one-half of the thickness of the paperboard from either side thereof.
Patents exist directed to the scoring of sheet material. Canadian Patent No. 198,546 patented Mar. 23, 1920 by P.C. Simmons provided a blank cutting machine. In this patent, the sheet was supported above the cutting die, and the cutting block was reciprocated vertically with respect to the cutting die. The cutting die was mounted on a stationary bed, and was adjustably mounted on a carrier by means of a series of set screws. This was no suggestion of relative adjustable movement between the cutting die and the cutting block.
Canadian Patent No. 710,631 patented Jun. 1, 1965 by T. Coy provided a die structure. In that patent, the bed had a plateau which supported a male die having a peripheral shearing edge. The female die comprised a steel rule supported by a wood blank. On a downward stroke, the female steel rule blanked a shaped piece when the steel rule contacted the plateau. There was no suggestion of relative adjustable movement between the plateau and the female steel rule.
Canadian Patent No. 1,312,542 patented Jan. 12, 1993 by J. V. W. Memmott et al provided a method and apparatus for cutting sheets of material. In that patent, a cutting board was provided against which the cutting die cut the plies of sheets of material. There was no suggestion of relative adjustable movement between the cutting die and the cutting board.
U.S. Pat. No. 2,939,358 patented Jun. 7, 1960 by E. W. Pearson provided a ledger blade adjustment means for a shear machine. This patent taught a horizontal adjustment of the lower knife with respect to the upper knife, in order to adjust the clearance. This was brought about by adjustment of the table assembly which was accomplished by positioning, within the upper portion of each of the slots, a bearing block for altering the spacing between the abutment lug and the edge defined by the upper end of the slot. The bearing block was welded to the upper end of the abutment lug. A bearing pad engaged the upper edge of the slot in spaced relationship to the bearing block, with one or both opposing surfaces being angled slightly. A wedge was adapted to be driven between the bearing block and the bearing pad. Controlled movement of the wedge in making adjustments was necessary, as the movement at one end of the front wall must be duplicated at the other end with substantial accuracy. However, there was no suggestion of direct, infinitely-variable control of relative spacing of the anvil against which the die blade cooperated to provide a reverse score cut.
U.S. Pat. No. 3,020,809 patented Feb. 13, 1962 by R. Guyer et al (and its corresponding Canadian Patent No. 655,713 issued Jan. 8, 1963 to R. Guyer et al), provided apparatus for die cutting paperboard. The aim of the patentee was to provide an extremely accurate control of the depth of cut. To achieve such aim, the patentee provided an apparatus which included a fixed platen having a metal die cutting plate thereon, the plate having a flat outer surface. A lower die was provided which included die cutting edges which projected from the cutting plate. A movable platen cooperated with the fixed platen, and a wooden base was supported by the movable platen, the wooden base including a die cutting rule projecting therefrom. Metal inserts were provided in the die, the metal inserts being supported upon the movable platen against which die cutting edges which projected through the die cutting plate may operate. These inserts were so arranged that the exposed surface of the inserts were spaced from the surface of the die cutting plate by a distance which was substantially equal to the thickness of the paperboard being cut. As a result, over the specific areas of the die in opposed relation to the die cutting edges on the fixed platen, an extremely accurate control of the depth of cut was alleged to be obtained. However, there was no teaching of an infinitely-variable control since the control steps were limited to the finite thickness of the metal inserts.
U.S. Pat. No. 3,170,342 patented Feb. 23, 1995 by R. H. Dounee provided a method of making cutting dies. A one-piece metallic plate had a photographically-registered representation of the male scoring and cutting elements in extremely shallow relief on its upper surface. The main surface of the plate was chemically etched away so that the scoring and cutting elements stood in slight relief. A complementary one-piece metallic female die was also provided which included cutting elements and scoring elements which co-acted with those of the male die to form the scores and cut-lines of the finished carton blank. These elements were also photo-composed and in very shallow relief to the chemically-etched background surface of the metallic plate. The patentee taught that the vertical gap between the male and female die plates when the press was on impression was adjustable to about a percentage of the over-all thickness of the board, to range from a slight overlap. Such vertical gap was adjusted by adhesively securing the male scoring die plate to a base of suitable thickness, or by attaching a thin sheet of resilient material to the etched background of the female plate by double sided adhesive tape. Thus, there was no teaching of an infinitely-variable control of such vertical gap, since the control steps were limited to the finite thickness of the securing member.
U.S. Pat. No. 3,292,513 patented Dec. 20, 1966 by C. E. Palmer, provided apparatus for scoring sheet material. The patentee provided a die assembly including a rectangular frame within which scoring members and cutting blades were received, which were held in predetermined space relationship by wooden spacer elements. The frame assembly included scoring platen members and a cutting platen member. The scoring platen members were resiliently supported by the resilient support member and the cutting platen member was independently and rigidly supported by the metal blocks. Thus, while a depth control was provided, such depth control was by way of resilient supporting means. There was no teaching of an infinitely-variable control of the depth.